Start by adding the yeast, water, and all of the biga starter to the bowl of the mixer and mix with the flat beater on low speed, if you don't have a stand mixer simply you can use spatula and large mixing bowls.
Gradually add the olive oil and then sea salt, when the dough becomes firmer, remove the flat beater and replace it with the dough hook and increase the speed of the mixer (Speed 2), and knead your dough for 15 minutes.
Lightly dust your work surface with flour and use the dough hook to place the dough on it. Fold the dough two times, and then put the right side on the left side of the dough, and repeat the process two times.
Grease a large bowl with oil and shape the dough into a round ball and place it in it, use a napkin or cling wrap to cover the dough to prevent it from drying out and place it in the oven for 1 hour.
Grease your hands with oil and place the dough in the pan and start spreading the dough all over the pan without leaving any gaps. Cover the pan with a napkin or cellophane and place it in the oven to rise for one 1 hour.
Take your pan out of the oven, place a baking sheet in the bottom of the oven and turn it on to 360℉ (180℃).
To Focaccia toppings: Mix the olive oil, black pepper and salt and spread the mixture on top of the dough, use your fingers to push and press the dough evenly over the bottom of the pan, then sprinkle with a pinch of rosemary.
Fill your electric kettle with water and turn it on.
Place the black pepper focaccia tray in the oven. Quickly pour hot water from the kettle (if you don't have a kettle, you can use ice cubes) over the bottom tray and turn off the oven.
Bake it at 360°C (180°F) for 40 minutes or until become set.
Remove black pepper Foccacia from the oven and enjoy on its own or as a sandwich.